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Subject: 
Re: Gear spacings.
Newsgroups: 
lugnet.robotics
Date: 
Wed, 8 Nov 2000 01:53:48 GMT
Original-From: 
Steve Baker <sjbaker1@AVOIDSPAMairmail.net>
Reply-To: 
sjbaker1@airmail.net{stopspam}
Viewed: 
1675 times
  
Jennifer Clark wrote:
> 
> J G Gregory wrote:
> 
> > So who is going to publish the super handbook on all these?  We really need
> > a "Technic Techniques" companion to the Mindstorms books.  Although things
> > like this are fairly trivial to compute, having a handy reference would be
> > nice.
> 
> Something else I've thought would be handy would be a program which would take
> as inputs the desired positions of the input and output axles in a gear train
> and the desired gear ratio. Space constraints in the form of "bricks" blocking
> off certain volumes of space would also be input. The program would then go off
> and compute all possible gear trains (if any) that fit the parameters. A degree
> of "fuzziness" could be built in that would allow, for example, variations of
> the desired gear ratio, and perhaps a factor could be specified stating the
> desired "perfectness" of the gear geometry.

Well, I think this is something you could divide into two parts:

  STEP 1:  Find all combination of gears that'll produce a gear ratio
           within some user-specified range using less than some specified
           number of gear wheels.

That's a simple problem to program - and it shouldn't produce *VAST* lists
of possible solutions so long as you don't let it use more than some reasonable
number of gears...there just aren't all that many combinations.

  STEP 2:  Find all possible ways of getting a particular set of gears to connect
           and axle at point A to another axle at point B.  This is also a simple
           problem since there are rarely more than a couple of choices for ways
           to connect one gear to it's neighbour...hence it shouldn't be hard to
           simply list all possible geometries for a particular gear train - and
           then reject all those that don't come close to connecting point A to
           point B.

Feeding the output of STEP 1 into STEP 2 should result in a program that would
run to completion in a reasonable amount of time.

Since the number of ways to connect A to B with a gear ratio within some specified
range will typically be quite small - I think it's up to the human brain to reject
those that don't fit around the obstacles.

Since STEP 1 and STEP 2 are both useful programs in their own rights, they should
probably be left as two separate programs.

> The problem is obviously of exponential complexity, but for small numbers of
> gears is no doubt managable without resorting to complex AI or constraint
> satisfaction techniques.

I don't think you need much more than brute force techniques.

> Of course, if it could also work out the necessary bracing to hold it all
> together, it would be even better :-)

Now *that* is hard!

--
Steve Baker   HomeEmail: <sjbaker1@airmail.net>
              WorkEmail: <sjbaker@link.com>
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Message is in Reply To:
  Re: Gear spacings.
 
(...) Something else I've thought would be handy would be a program which would take as inputs the desired positions of the input and output axles in a gear train and the desired gear ratio. Space constraints in the form of "bricks" blocking off (...) (26 years ago, 7-Nov-00, to lugnet.robotics)

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